About Hadrian's Wall:
Hadrian came to Britain in 122 AD and was the first to build a wall 80 milles long from sea to sea to separate Barbarians from the Romans. The construction of the building took at least six years to complete. The wall was a defensive fortification that marked the northwest frontier of the Roman Empire for three centuries, it's thought to have taken an army of 15,000 men to complete it. The majority of the wall was made from stone, although some portions were fabricated from grass. Small forts called milecastles were established at every Roman mille, along the wall, and two observation tumets were placed between each milecastles too, among down larger forts along the wall's length where soldiers were stationed. Hadrian served as emperor from 117 until his death in 138. Hadrian’s death in AD 138 brought a new emperor to power. The emperor Antoninus Pius abandoned Hadrian’s Wall and moved the frontier up to the Forth–Clyde isthmus, where he built a new wall, the Antonine Wall.